The present invention concerns a system for evaluating the soot loading state of depollution means integrated in an exhaust line of a motor vehicle engine.
Such an engine can be associated with common rail means for the supply of fuel into the cylinders thereof, according to at least one post-injection.
Such a post-injection is, in a standard manner, an injection of fuel after the high dead center of the cylinder under consideration.
These supply means are adapted to implement, in isocouple, through modification of parameters for controlling the operation of the engine, different regeneration strategies making it possible to obtain different thermal levels in the exhaust line.
Thus, for example, supply means implementing regeneration strategies called normal, level 1, level 2, and/or over-calibrated level 2 strategies, have already been proposed.
Indeed, it is known that, to ensure the regeneration of depollution means such as a particle filter, the soot trapped therein are burned thanks to the thermal energy provided by the engine and to the exotherm obtained by the conversion of the HC and of the CO on means forming oxidation catalyst, placed, for example, upstream of the particle filter.
This combustion can be assisted by a catalyzing element mixed with the soot, coming, for example, from a regeneration assistance additive, mixed with the fuel for the supply of the engine, or by a catalyst deposited directly on the walls of the particle filter (catalyzed particle filter).
The higher the thermal levels in the exhaust line at the inlet of the particle filter, the shorter the duration of the filter regeneration.
One of the main problems in connection with the use of a particle filter is its regeneration. Indeed, in the course of the use of a vehicle equipped with a particle filter, this filter clogs up. The different residues which pile up therein can have mainly four different origins. Indeed, the residues can be formed by metallic elements coming from the engine or from the exhaust line or by particles which were not filtered at the intake. Other residues can be formed by ashes coming from the lubricant of the engine or by ashes coming from the fuel supplying this engine. Finally, other residues can be formed by combustion residues of a regeneration assistance additive. Indeed, it is known that such additives can be used and can be mixed with the fuel for the supply of the engine to lower the combustion temperature of the soot trapped in the particle filter.
In a particle filter design using a regeneration assistance additive making it possible to promote the combustion of the soot, these four elements accumulate in the filter. In the case where such an additive is not used, for example, in the case of impregnated or catalyzed particle filters, only three of these elements are present in the filter, which reduces the volume of residues accumulated for a given mileage traveled.
However, whatever the design used, the particle filter clogs up progressively, thus reducing the volume available for the storage of the particles. As a result, to preserve the good thermo-mechanical resistance of the filter, it is necessary to regenerate this filter more and more often, which translates into an increase of the over-consumption of fuel in connection with the particle filter in the case, for example, where the regeneration is performed by using post-injections or a burner and by a dilution of the lubrication oil of the engine by the post-injected fuel with a risk of engine breakage.
Further, the reduction of the useful soot storing volume generates higher and higher head losses at the boundaries of the filter, which translates both into an increase of the fuel consumption of the vehicle outside of the regeneration phases and into a risk of engine break-up, for example, if the differential pressure at the boundaries of the filter is too high and provokes a reopening of the valves.
It is thus necessary to regenerate the filter after a certain mileage traveled when the volume available for the storage of the particles becomes too low.
Two vehicles having driven the same number of kilometers can have accumulated amounts of residues very different from each other, as a function of the type of driving of these vehicles. For example, city driving with an average fuel consumption of 10 liters for 100 kilometers generates 67% additive consumption residues more than open road driving with an average consumption of 6 liters for 100 kilometers. It is then appropriate to optimize the frequency of regeneration of the particle filter by evaluating as best as possible the loading state of this type of depollution means.